1. Field of the Invention
This invention relates to a wireless communication terminal device such as a cellular phone, especially relates to a wireless communication terminal device with an antenna housed within a housing.
2. Description of the Related Art
(First Related Art)
Traditionally, in order to assure the antenna characteristic (such as sensitivity), the antenna of the wireless communication terminal device such as a cellular phone was structured so as to be extended externally from the inside of a housing. Although some space is required, the main part of the antenna is externally exposed so that the internal components had little effect on the antenna. Inversely, the antenna also had little limiting effect on the inside of the housing.
Recently, in the wireless communication terminal device such as the cellular phone, for the purpose of miniaturization and improving portability, in many cases, an internal antenna has been adopted. For example, JP-A-2000-134020 discloses the wireless communication terminal device having an internal antenna serving as a chip antenna formed on a flexible board fixed to a shielding case.
However, in the wireless communication terminal device adopting the internal antenna, if another metallic member exists around the antenna, this metallic member may hinder the wireless communication function of the antenna. Further, if the antenna is incorporated at a position, enabling the hindrance to be avoided, the communication would be large-scaled. This led the first problem that it is difficult to assure the space for arranging the antenna within the housing.
(Second Related Art)
There were some wireless communication terminal devices such as a cellular phone in which a user extends an extendable antenna loaded therein in its longitudinal direction and thereafter starts communication such as a telephone call.
However, such an extendable antenna increases the length of the wireless communication terminal device by the extending degree of the antenna, which was an obstruction against making the wireless communication terminal device compact. In order to obviate such inconvenience, a wireless communication terminal device has been proposed which is provided with an internal antenna in place of the above extendable antenna and so can be maintained in compact state during communication also (For example, see JP-A-2003-101623, JP-A-11-312912, and JP-A-10-163748.).
However, in the wireless communication terminal device provided with the internal antenna, the antenna is arranged in the vicinity of the ground (metallic area communicated with a reference potential) on a circuit board within a housing. This led to the second problem that the antenna gain is deteriorated as compared with the wireless communication terminal device provided with the extendable antenna.